1. Field of the Invention
The present invention relates to a wireless communication system and a user equipment (UE) providing wireless communication services, and more particularly, a method of minimizing an unnecessary MSI (MCH Scheduling Information) reception by a terminal (UE) during a reception of a MBMS (Multimedia Broadcast/Multicast Service) service in an Evolved Universal Mobile Telecommunications System (E-UMTS), a Long Term Evolution (LTE) system, and a LTE-Advanced (LTE-A) system that have evolved from a Universal Mobile Telecommunications System (UMTS).
2. Description of the Related Art
The LTE system is a mobile communication system that has evolved from a UMTS system, and the standard has been established by 3rd Generation Partnership Project (3GPP), which is an international standardization organization.
FIG. 1 is a view illustrating the network architecture of an LTE system, which is a mobile communication system to which the related art and the present invention are applied.
As illustrated in FIG. 1, the LTE system architecture can be roughly classified into an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) and an Evolved Packet Core (EPC). The E-UTRAN may include a user equipment (UE) and an Evolved NodeB (eNB, base station), wherein the connection between UE-eNB is called a Uu interface, and the connection between eNB-eNB is called an X2 interface. The EPC may include a Mobility Management Entity (MME) performing a control-plane function and a Serving Gateway (S-GW) performing a user-plane function, wherein the connection between eNB-MME is called an S1-MME interface, and the connection between eNB-S-GW is called an S1-U interface, and both connections may be commonly called an S1 interface.
A radio interface protocol is defined in the Uu interface which is a radio section, wherein the radio interface protocol is horizontally comprised of a physical layer, a data link layer, a network layer, and vertically classified into a user plane (U-plane) for user data transmission and a control plane (C-plane) for signaling transfer. Such a radio interface protocol can be typically classified into L1 (first layer) including a PHY layer which is a physical layer, L2 (second layer) including MAC/RLC/PDCP layers, and L3 (third layer) including a RRC layer as illustrated in FIGS. 2 and 3. Those layers exist as a pair in the UE and E-UTRAN, thereby performing data transmission of the Uu interface.
FIGS. 2 and 3 are exemplary views illustrating the control plane and user plane architecture of a radio interface protocol between UE and E-UTRAN in an LTE system, which is a mobile communication system to which the related art and the present invention are applied.
The physical layer (PHY) which is a first layer provides information transfer services to the upper layers using a physical channel. The PHY layer is connected to the upper Medium Access Control (MAC) layer through a transport channel, and data between the MAC layer and the PHY layer is transferred through the transport channel. At this time, the transport channel is roughly divided into a dedicated transport channel and a common transport channel based on whether or not the channel is shared. Furthermore, data is transferred between different PHY layers, i.e., between PHY layers at the transmitter and receiver sides.
Various layers exist in the second layer. First, the Medium Access Control (MAC) layer serves to map various logical channels to various transport channels, and also performs a logical channel multiplexing for mapping several logical channels to one transport channel. The MAC layer is connected to an upper Radio Link Control (RLC) layer through a logical channel, and the logical channel is roughly divided into a control channel for transmitting control plane information and a traffic channel for transmitting user plane information according to the type of information to be transmitted.
The Radio Link Control (RLC) layer of the second layer manages segmentation and concatenation of data received from an upper layer to appropriately adjust a data size such that a lower layer can send data to a radio section. Also, the RLC layer provides three operation modes such as a transparent mode (TM), an un-acknowledged mode (UM) and an acknowledged mode (AM) so as to guarantee various quality of services (QoS) required by each radio bearer (RB). In particular, AM RLC performs a retransmission function through an automatic repeat and request (ARQ) function for reliable data transmission.
A Packet Data Convergence Protocol (PDCP) layer of the second layer performs a header compression function for reducing the size of an IP packet header which is relatively large in size and contains unnecessary control information to efficiently transmit IP packets, such as IPv4 or IPv6, over a radio section with a relatively small bandwidth. Due to this, information only required from the header portion of data is transmitted, thereby serving to increase the transmission efficiency of the radio section. In addition, in the LTE system, the PDCP layer performs a security function, which includes ciphering for preventing the third person's data wiretapping and integrity protection for preventing the third person's data manipulation.
A radio resource control (RRC) layer located at the uppermost portion of the third layer is only defined in the control plane. The RRC layer performs a role of controlling logical channels, transport channels and physical channels in relation to configuration, re-configuration, and release of Radio Bearers (RBs). Here, the RB denotes a logical path provided by the first and the second layers for transferring data between the UE and the UTRAN. In general, the establishment of the RB refers to a process of stipulating the characteristics of protocol layers and channels required for providing a specific service, and setting each of the detailed parameter and operation method thereof. The RB is divided into a signaling RB (SRB) and a data RB (DRB), wherein the SRB is used as a path for transmitting RRC messages in the C-plane while the DRB is used as a path for transmitting user data in the U-plane.
Hereinafter, a description of MBMS (Multimedia Broadcast/Multicast Service) will be given. In order to provide the MBMS service to a terminal (UE), in general, the wireless network may provide the MBMS Control Channel (MCCH) and the MBMS Traffic Channel (MTCH) for an MBMS service. The MCCH is used for transmitting MBMS control information to a terminal. The MTCH is used for transmitting the MBMS service to the terminal. The MBMS service is comprised of one session or a plurality of sessions, and only one session should exist for single time period (or duration). The wireless network may transmit an MBMS notification message in order to inform a session start of the MBMS service or a change of the MBMS control information. The notification message may be transmitted via the MCCH channel. Meanwhile, through the MBMS Indicator Channel (MICH), the wireless network notifies the terminal whether or not a MBMS notification message or control information for a specific service has been changed (modified).
In a conventional art, the terminal (UE) must read MCH scheduling information (MSI) in every MCH scheduling period in order to receive a certain MBMS service. However, since a MBMS data can be transmitted intermittently due to its traffic characteristic, in some case, some MBMS data may not be transmitted in the MCH scheduling period. Therefore, if the terminal always wakes in every MCH scheduling period to receive the MSI, this will cause an unnecessary battery consumption of the terminal.